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United States Patent |
5,551,468
|
Lemke
|
September 3, 1996
|
Fluidic density control for chlor alkali cells
Abstract
The density of a caustic solution is reduced by automatically adding water
to the caustic solution when the specific gravity of the caustic solution
is unacceptably high. The mechanism consists of a flow control valve that
is controlled by an switch that monitors the position of a hydrometer. The
switch is activated when the density of the caustic solution rises to
unacceptable levels, causing the hydrometer to rise and activate the
switch. The switch controls a valve that opens and allows water to enter
the caustic solution reservoir, thereby diluting the caustic solution.
When sufficient water has been added to the caustic, the hydrometer drops
and the switch is deactivated, thereby closing the valve that allows water
to enter the caustic solution reservoir. Excess caustic solution leaves
the reservoir through an overflow on the reservoir.
Inventors:
|
Lemke; Chris A. (3727 N. Hughes Ave., Fresno, CA 93722)
|
Appl. No.:
|
380236 |
Filed:
|
January 30, 1995 |
Current U.S. Class: |
137/3; 137/91 |
Intern'l Class: |
G05D 021/02 |
Field of Search: |
137/3,91
|
References Cited
U.S. Patent Documents
2543522 | Feb., 1951 | Cohen | 137/91.
|
3089502 | May., 1963 | Davidson et al. | 137/91.
|
4422085 | Dec., 1983 | Sumitomo et al. | 137/91.
|
4601306 | Jul., 1986 | Engelhardt et al. | 137/91.
|
4825228 | Apr., 1989 | Gloeckler | 137/93.
|
4899774 | Feb., 1990 | Keller | 137/4.
|
5013488 | May., 1991 | Abadi et al. | 137/91.
|
Primary Examiner: Hepperle; Stephen M.
Parent Case Text
This application is a continuation of Ser. No. 177,760, filed Jan. 4, 1994,
now abandoned.
Claims
Now that the invention has been described, what is claimed is:
1. An apparatus for regulating concentration of a caustic in a chlor-alkali
cell system containing, a caustic reservoir holding said caustic of a
predetermined concentration, a dilution water reservoir containing a
dilution water for reducing concentration of said caustic to said
predetermined concentration, a conduit interconnecting said dilution water
reservoir and said caustic reservoir, and a control valve governing said
conduit interconnecting said dilution water reservoir and said caustic
reservoir, said regulating apparatus comprising:
a caustic reservoir inlet connected to said conduit in said caustic
reservoir;
an object body;
said object body being floatingly arranged in said caustic reservoir and
being positionally adjustable in said caustic reservoir in response to
variations in the concentration of said caustic in said caustic reservoir;
a housing means for guiding said object body for upward and downward
directed movements in said caustic reservoir to said variations in said
concentration of said caustic in said caustic reservoir;
said housing means being connected to a switch means;
said housing means containing an object body stop firmly attached at a
predetermined cross-section of said housing means;
said object body stop submerged in said caustic in said caustic reservoir;
said object body stop having a predetermined number of perforations
allowing unrestricted flow and mixing of said caustic in said housing
means;
said switch means operatively associated with a predetermined position of
said object body and operatively connected to said control valve;
said object body is upwardly restricted by said object body stop at said
predetermined position operatively associated with said switch means; and
said object body, in said predetermined position in said housing means
acting upon said switch means and thereby operating said control valve for
passing said dilution water from said dilution water reservoir to said
caustic reservoir until said concentration of said caustic in said caustic
reservoir is reduced to said predetermined concentration.
2. The apparatus as defined in claim 1, wherein said caustic reservoir
inlet is positioned at a predetermined location within said caustic
reservoir directing sufficient mixing of said dilution water with said
caustic in said caustic reservoir.
3. The apparatus as defined in claim 1, wherein said switch means
constitute a photoelectric switch.
4. An apparatus for regulating concentration of a liquid comprising:
a housing means connected to a reservoir containing said liquid of a
predetermined concentration;
said housing means being positionally attached to said reservoir allowing
flow of said liquid through said housing means;
a dilution reservoir containing a dilution liquid for reducing
concentration of said liquid to said predetermined concentration;
a conduit interconnecting said dilution reservoir and said reservoir;
a control valve governing said conduit interconnecting said dilution
reservoir and said reservoir;
a reservoir inlet connected to said conduit in said reservoir;
an object body;
said object body being floatingly arranged in said housing means and being
positionally adjustable for upward and downward directed movements in said
housing means in response to variations in the concentration of said
liquid in said reservoir;
said housing means being connected to a switch means;
said housing means containing an object body stop firmly attached at a
predetermined cross-section of said housing means;
said object body stop submerged in said liquid in said housing means;
said object body stop having a predetermined number of perforations
allowing unrestricted flow and mixing of said liquid in said housing
means;
said switch means operatively associated with a predetermined position of
said object body and operatively connected to said control valve; and
said object body is upwardly restricted by said object body stop at said
predetermined position operatively associated with said switch means;
said object body, in said predetermined position in said housing means
acting upon said switch means and thereby operating said control valve for
passing said dilution liquid from said dilution reservoir to said
reservoir until said concentration of said liquid in said reservoir is
reduced to said predetermined concentration.
5. The apparatus as defined in claim 4, wherein said reservoir inlet is
positioned at a predetermined location within said reservoir directing
sufficient mixing of said dilution liquid with said liquid in said
reservoir.
6. The apparatus as defined in claim 4, wherein said switch means
constitute a photoelectric switch.
7. A method of regulating concentration of a caustic in a chlor-alkali cell
system containing, a caustic reservoir holding said caustic of a
predetermined concentration, a dilution water reservoir containing a
dilution water for reducing concentration of said caustic to said
predetermined concentration, a conduit interconnecting said dilution water
reservoir and said caustic reservoir, a caustic reservoir inlet, a control
valve governing said conduit interconnecting said dilution water reservoir
and said caustic reservoir, and a switch governing said control valve,
said method comprising the steps of:
positionally adjusting an object body in buoyant response to the
concentration of said caustic in said caustic reservoir where said object
body is positionally associated to an object body stop submerged in said
caustic at a predetermined reference datum;
sensing a predetermined position of said object body in said caustic
reservoir which corresponds to said predetermined reference datum
indicative of a caustic concentration that exceeds said predetermined
concentration of said caustic; and
regulating said caustic concentration when said predetermined position of
said object body activating said switch governing said control valve and
passing said dilution water from said dilution water reservoir through
said control valve into said caustic reservoir as long as said caustic
concentration of said caustic in said caustic reservoir exceeds said
predetermined concentration.
8. The method as defined in claim 7, further including the steps of:
arranging said caustic reservoir inlet at a predetermined location within
said caustic reservoir directing sufficient mixing of said dilution water
with said caustic in said caustic reservoir.
Description
BACKGROUND-FIELD OF THE INVENTION
This invention relates, generally, to improvements in electrolytic cells
that generate chlorine gas and caustic solutions and delivers those
products to a drinking water supply system, wastewater treatment system,
industrial processing system, or a swimming pool. More particularly, it
relates to an improved means for controlling the density of the caustic
liquid therein.
BACKGROUND-DESCRIPTION OF PRIOR ART
U.S. Pat. No. 4,899,774 (1990) and the references to record therein are
believed to represent the most relevant prior art to this disclosure.
Chlor-alkali cells provide an electromotive force to split the chemical
bond between sodium and chlorine elements of ordinary sodium chloride
(table salt). Chlorine is used as a disinfectant in water, wastewater, and
swimming pool applications. Chlorine is also used as an oxidant in water,
wastewater, and industrial treatment processes. The sodium produced from
the process combines with water to form sodium hydroxide (caustic) which
is used as a disinfectant and pH control chemical in water, wastewater and
swimming pool applications. Caustic is also used as a cleansing chemical
agent in several processes.
The chlor-alkali process in its simplest form, employs the use of an anode
electrode, cathode electrode, and a membrane placed between the two
electrodes that provides isolation of the caustic and salt brine. The
cathode portion of the cell provides a continuous influx of sodium into
the caustic, thereby increasing the concentration of the caustic. A high
concentration of caustic will cause excessive wear on the membrane.
Therefore, it is desirable to keep the concentration of the caustic at a
level that promotes the necessary electrical conductivity, and low enough
to prevent premature wear of the membrane.
One method to measure the concentration of caustic is to determine the
density of the caustic. The most common method to determine density is by
specific gravity comparison using a hydrometer. The prior art utilizes a
specially designed hydrometer of known specific gravity to determine the
density of caustic. Buoyant forces imposed on the hydrometer cause the
hydrometer to rise when the concentration of caustic increases. The
hydrometer rises to an elevation that intercepts a horizontally projected
stream of water to dilute the caustic solution.
The claims in the prior art describe an apparatus that prevents the density
of the caustic from exceeding a high unacceptable density limit. As
mentioned previously, this is important from the standpoint of membrane
maintenance of the chlor-alkali cell operation. The claims however, will
not allow the cell to achieve density equilibrium until after the nozzle
that produces the horizontally projected stream of water and the bypass
collection port are submerged by the caustic. This is because the claims
do not describe how the elevation of the specially designed hydrometer is
maintained in necessary reference to the elevation of the horizontal
dilution stream.
The apparatuses and method described in the prior an claims would provide
dilution to the caustic since the hydrometer would rise and intercept the
horizontally projected dilution stream, and therefore deflect a portion of
the dilution stream into the caustic. However, the liquid elevation of the
caustic would increase, thereby changing the reference elevation
associated with the specially designed hydrometer. Since the elevation of
the caustic liquid surface is increased, the hydrometer will now intercept
the horizontally projected dilution stream at a lower density limit.
Eventually, the dilution cycle would continue until enough dilution water
is added causing the elevation of the caustic liquid surface to intercept
the elevation of the horizontally projected dilution stream. This
condition would make the specially designed hydrometer ineffective for its
designed purpose, and render the cell nearly inoperative due to the
decreased catholyte electric conductivity.
Although the specification of the prior art illustrates means to maintain
the necessary reference elevation between the caustic liquid level and the
horizontally projected dilution stream, there is no assurance that the
apparatuses and method claimed in the prior art will maintain the
necessary lower density limit. This is essential in terms of maintaining
the necessary electrolyte conductivity for the chlor-alkali cell
operation.
The dilution water added to the caustic should be softened to remove the
calcium that impairs the function of the membrane (thus impairing the
function of the chlor-alkali cell). The prior art apparatus employs a
continuously flowing source of dilution water, whereby a significant
portion of the dilution water bypasses the caustic reservoir and is not
used for dilution purposes. The prior art indicates that the water
bypassing the dilution apparatus is recycled. If the water is recycled
back to the dilution mechanism, the recycled water must be re-pressurized
to obtain the necessary horizontal projection of the dilution stream. The
cost of recycling the dilution water solely for this purpose is generally
cost prohibitive. Also, the cost of continuously providing a treated
source of water to the prior art dilution apparatus is great when compared
to a system that employs 100 percent of the dilution water (no bypass)
into the caustic reservoir.
The apparatus described in the prior art utilizes a nozzle to develop the
horizontally projected solution stream. The small orifice of the nozzle is
subject to plugging by small particles in the dilution water source,
especially if the source of water is untreated. A partially plugged nozzle
may prevent the horizontally projected stream from reaching the bypass
destination (collection reservoir) and enter directly into the caustic
reservoir, thus prematurely diluting the caustic. A fully plugged nozzle
will remove the dilution source from the apparatus causing the density of
the caustic to exceed the high unacceptable limit. Either scenario
outlined above is undesirable from the standpoint of cell operation and
membrane maintenance.
The prior art apparatus distributes the deflected dilution water at the
surface of the caustic solution in the area immediately surrounding the
hydrometer. Considering that the density of the dilution water is less
than the density of the caustic, the dilution water added at the surface
would tend to remain at the surface. The variable density gradient
produced by this method is undesirable from the standpoint of membrane
maintenance and cell operation. Mixing of the caustic would need to be
employed to assure homogeneous density distribution throughout the entire
caustic reservoir. This is needed for the hydrometer to determine the
actual density of the caustic in the cell. The optimum location to add the
dilution water would be near the bottom of the cell. The lower density
dilution water would be more buoyant than the higher density caustic
liquid causing the lower density liquid to rise in the cell, thus creating
natural mixing and a virtually homogeneous density distribution.
When directly using the chlor-alkali process for supplying chemicals to a
public water supply system, it is important to note that many state and
local regulations do not allow the introduction of recycled water into a
water system without appropriate treatment. The dilution water apparatus
described in the prior art provides an entry point of potential
contamination either through natural means or by sabotage. A sealed
chlor-alkali cell with no bypass or recycled dilution water would be
desired.
In summary, the apparatus described in the prior art employs a unique
method to introduce dilution water into a caustic solution. However,
several improvements are needed to make the apparatus safe and reliable.
The following are disadvantages known to exist with the prior art.
(a) There is no assurance that the prior art will employ the reference
means between the hydrometer and the horizontally projected dilution
stream to maintain the necessary lower density limit of a caustic
solution.
(b) The cost of supplying a "calcium free" dilution stream can be costly
when considering the significant portion of the dilution stream that
bypasses the caustic reservoir.
(c) The nozzle used to create the horizontally projected solution stream is
subject to plugging by small particles in the dilution water. Partial
plugging will cause the dilution stream to enter directly into the caustic
reservoir causing premature caustic dilution. Total nozzle plugging will
eliminate the dilution stream causing the density of the caustic to exceed
the unacceptable density limit.
(d) The dilution water is added to the surface of the caustic liquid. Since
the density of the dilution water is less than the density of caustic, a
non-homogeneous density gradient will be experienced if mixing is not
employed. The concentration of caustic output and the operation of the
system will be inconsistent.
(e) The generation of a recycled water often requires further treatment of
the water to be recycled in drinking water systems. The dilution water
bypassing the dilution apparatus provides an entry point of potential
contamination either by natural means or by sabotage.
OBJECTS AND ADVANTAGES
Accordingly, several objects and advantages of my invention are:
(a) to automatically maintain a desirable density range of a caustic
solution in a chlor-alkali cell where the cell promotes an increasing
dynamic density flux upon the caustic solution;
(b) to allow 100 percent of all water available for dilution to be added to
the caustic solution only when dilution water is needed, where no dilution
water is bypassed, wasted, or recycled, thus reducing the cost of
providing calcium removal and other required treatment to the dilution
water;
(c) to provide a sufficiently sized dilution water orifice that reliably
controls the desired flow of dilution water added to the caustic solution;
(d) to add dilution water to a caustic solution at the location that
promotes natural mixing, thereby achieving a homogeneous caustic solution;
(e) to reduce the potential of system contamination by providing enclosures
that seal all components of the invention from the outside environment.
Further objects and advantages will become apparent from a consideration of
the ensuing description and drawings.
DESCRIPTION OF DRAWINGS
For a fuller understanding of the nature and objects of the invention,
reference should be made to the following detailed description, taken in
consideration with the accompanying drawings in which:
FIGS. 1 and 1A are schematic representations of the invention showing a
electrolytic cell containing a caustic liquid, a hydrometer apparatus
measuring the density of the caustic liquid, and a dilution water control
apparatus that controls the flow of dilution water into the electrolytic
cell. FIG. 1 illustrates an electrolytic cell with caustic at a desirable
density range. FIG. 1A illustrates the flow of dilution water into an
electrolytic cell with caustic at an unacceptable high range.
FIGS. 2 and 2A are illustrations of a piston type hydrometer apparatus
disposed in a caustic solution. FIG. 2 illustrates the position of the
hydrometer when the density of the caustic is within an acceptable range.
FIG. 2A illustrates the position of the hydrometer when the density of the
caustic is within an unacceptable range.
FIGS. 3 and 3A are illustrations of an emerged body type hydrometer
apparatus disposed in a caustic solution. FIG. 3 illustrates the position
of the hydrometer when the density of the caustic is within an acceptable
range. FIG. 3A illustrates the position of the hydrometer when the density
of the caustic is within an unacceptable range.
FIGS. 4 and 4A are illustrations of a photoelectric switch contained within
a housing that provides the necessary communication with the hydrometer
apparatus. FIG. 4 illustrates an open circuit that occurs when the
hydrometer is located at a position illustrated in FIG. 3. FIG. 4A
illustrates a closed circuit that occurs when the hydrometer is located at
a position illustrated in FIG. 3A.
FIGS. 5 and 5A are illustrations of a snap action switch contained within a
housing that provides the necessary communication with the hydrometer
apparatus. FIG. 5 illustrates an open circuit that occurs when the
hydrometer is located at a position illustrated in FIG. 3. FIG. 5A
illustrates a closed circuit that occurs when the hydrometer is located at
a position illustrated in FIG. 3A.
FIGS. 6 and 6A are detailed illustrations of the invention featuring a
piston type hydrometer apparatus, and a photoelectric switch. FIG. 6
illustrates the position of the hydrometer when the density of the caustic
is within an acceptable range whereby no dilution water is added to the
caustic. FIG. 6A illustrates the position of the hydrometer when the
density of the caustic is at an unacceptable high range, whereby the
hydrometer activates a switch that closes an electrical circuit that
causes a valve control to open a valve that allows dilution water to enter
the caustic reservoir.
FIGS. 7 and 7A are detailed illustrations of the invention featuring an
emerged body type hydrometer apparatus, and a photoelectric switch. FIG. 7
illustrates the position of the hydrometer when the density of the caustic
is within an acceptable range whereby no dilution water is added to the
caustic. FIG. 7A illustrates the position of the hydrometer when the
density of the caustic is at an unacceptable high range, whereby the
hydrometer activates a switch that closes a circuit that causes a valve
control to open a valve and allow dilution water to enter the caustic
reservoir.
FIGS. 8 and 8A illustrate a multiple dilution water control apparatuses for
a single hydrometer apparatus. FIG. 8 illustrates photoelectric switches
in communication with a piston type hydrometer apparatus. FIG. 8A
illustrates photoelectric switches in communication with an emerged body
type hydrometer apparatus.
LIST OF REFERENCE NUMERALS
______________________________________
10 catholyte reservoir
12 caustic
14 outlet 14A outlet port
16 inlet 20 hydrometer apparatus
20A piston type hydrometer
20B emerged body type hy-
21 emerged body drometer
22 enclosed body 21' higher density emerged
24 removable stem body
25B access port 23 emerged body enclosure
27 emerged body stop
25A access port
30 opening 26 hydrometer sleeve hous-
34 switch containment hous-
ing
ing 28 liquid
35 dilution water control re-
32 sealed threaded
ference elevation connection
35' secondary dilution water
control reference elevation
36 hydrometer activation re-
ference elevation
37 activation differential
elevation
38 hydrometer differential
elevation
39 hydrometer base reference
elevation
40 dilution water control
42 valve
apparatus 46 energy source
44 valve control 50 switch
48 circuit 50B snap action switch
50A photoelectric switch
52 photoelectric light
51 switch body source
53 activation lever arm
54 photoelectric light
56 retroreflective target receiver
60 dilution water reservoir
58 light beam
64 dilution water inlet
62 dilution water
______________________________________
SUMMARY
The present invention employs a hydrometer disposed in the caustic solution
as in the earlier patent, but the need for an unreliable dilution stream
with bypassed or recycled water is eliminated. Instead, means are provided
to dilute the caustic by mechanisms that allow all the dilution water
available to enter the caustic chamber only when needed, allow dilution
water to be added at a location that promotes natural mixing, and provide
an orifice controlling the flow of dilution water entering the caustic
chamber of sufficient size to prevent plugging by small particles.
Specifically, when the density of the caustic solution increases, a
hydrometer apparatus raises and activates a switch on the dilution water
control system. An activated switch opens a control valve on a pipeline
that allows dilution water to enter the caustic reservoir. As the water
enters the reservoir, the caustic is diluted, causing the hydrometer
apparatus to drop. As the hydrometer drops the switch is de-activated,
causing the control valve on the dilution water pipeline to close.
Therefore, the invention allows precise, reliable control of adding
dilution water to a caustic influenced by a dynamic density gradient.
It is therefore understood that the primary objective of this invention is
to provide an economically reliable automatic fluid density control system
for chlor-alkali and similar electrolytic cells.
DESCRIPTION OF INVENTION
The configuration of the invention can partake several forms. It is the
intention of this narrative to describe a few of the forms in detail.
A schematic representation of the invention is illustrated in its simplest
form by FIG. 1. As shown in FIG. 1, the invention is comprised of a
hydrometer apparatus 20 that measures density of a caustic 12 contained in
a catholyte reservoir 10. Hydrometer apparatus 20 is in communication with
a dilution water control apparatus 40 that regulates flow of a dilution
water 62 from a dilution water reservoir 60 into catholyte reservoir 10
through inlet 16. Displaced caustic 12 in catholyte reservoir 10 exits
through an outlet 14.
Dilution water control apparatus 40 is comprised of a valve 42, operated by
a solenoid or motorized valve control 44, powered by an energy source 46,
supplied by a circuit 48, having a switch 50. Valve 42 is closed with
energy source 46 removed from circuit 48 by open switch 50 (FIG. 1). Valve
42 is open with energy source 46 supplied to valve control 44 through
circuit 48 by closed switch 50 (FIG. 1A). Valve 42 is connected in-line
with inlet 16 that provides means for dilution water 62 to enter catholyte
reservoir 10.
FIGS. 2 and 3 illustrate two variations of hydrometer apparatus 20 mounted
to catholyte reservoir 10. FIG. 2 illustrates a piston type hydrometer 20A
mounted directly within the interior of catholyte reservoir 10. FIG. 3
illustrates an emerged body type hydrometer 20B attached to the exterior
of catholyte reservoir 10. Piston type hydrometer 20A can also be mounted
to the exterior of catholyte reservoir 10 in a similar fashion to emerged
body type hydrometer 20B.
Piston type hydrometer 20A shown in FIG. 3 is comprised of a removable stem
24 attached to an enclosed body 22 contained in a hydrometer sleeve
housing 26. A liquid 28 is contained within enclosed body 22 providing the
desired density rating of piston type hydrometer 20A. Liquid 28 is added
into enclosed body 22 through an opening 30 where removable stem 24 is
attached to top of enclosed body 22 by a sealed threaded connection 32.
Therefore, the interior of piston type hydrometer 20A is isolated from the
exterior environment.
Piston type hydrometer 20A is suspended in caustic 12 where gravitational
forces caused by the weight of piston type hydrometer 20A and the
associated buoyant forces produced by caustic 12 are equal. Hydrometer
sleeve housing 26 provides virtually frictionless containment of piston
type hydrometer 20A allowing unencumbered vertical movement of piston type
hydrometer 20A in caustic 12. Buoyant forces imposed on piston type
hydrometer 20A by caustic 12 provide a hydrometer differential elevation
38 between a hydrometer base reference elevation 39 and a hydrometer
activation reference elevation 36. Hydrometer base reference elevation is
maintained by outlet 14 connected to catholyte reservoir 10. Differential
elevation 38 therefore varies with density of caustic 12.
Hydrometer sleeve housing 26 is fixed below a switch containment housing 34
providing a dilution water control reference elevation 35. An activation
differential elevation 37 is developed between dilution water control
reference elevation 35 and hydrometer base reference elevation 39.
Activation differential elevation 37 remains constant and represents the
vertical distance at which piston type hydrometer 20A extends above the
liquid surface of caustic 12 when density of caustic 12 is at the maximum
desirable density limit (FIG. 2A). Therefore hydrometer differential
elevation 38 and activation differential elevation 37 are the same when
maximum desirable density limit of caustic 12 is reached.
Emerged body type hydrometer 20B shown in FIG. 3 is comprised of an emerged
body 21 contained in an emerged body enclosure 23. Emerged body enclosure
23 provides virtually frictionless containment of emerged body 21 allowing
unencumbered vertical movement of emerged body 21 within emerged body 23.
Switch containment housing 34 is fastened to emerged body enclosure 23 at
an elevation higher than the top elevation of emerged body 21 at its
lowest position within emerged body enclosure 23 (FIG. 3). Emerged body
enclosure 23 is constructed of a transparent plastic or glass allowing
clear visual observation of emerged body 21. Emerged body 21 is
non-transparent and is composed of a material with the same specific
gravity of caustic 12 at the maximum desirable density limit.
Emerged body type hydrometer 20B is fastened to catholyte reservoir 10 by
an access port 25A and an access port 25B. Access ports 25A and 25B
provide open enclosure with the interior of catholyte reservoir 10 thus
allowing entry of caustic 12 into emerged body enclosure 23. An outlet
port 14A is fixed to the upper portion of emerged body enclosure 23
providing an outlet for displaced caustic 12 in catholyte reservoir 10 and
emerged body enclosure 23. An emerged body stop 27 is fixed within the
horizontal cross-sectional interior of emerged body enclosure 23 slightly
above dilution water control reference elevation 35 provided by switch
containment housing 34. Emerged body stop 27 is perforated allowing flow
of caustic 12 through emerged body enclosure 23 when emerged body 21 is
located at any location below emerged body stop 27. Liquid level elevation
of caustic 12 exceeds dilution water control reference elevation 35.
Buoyant forces imposed on emerged body 21 by caustic 12 cause emerged body
21 to rise when density of caustic 12 exceeds the maximum desirable
density limit. Rising of emerged body 21 is stopped by emerged body stop
27 at the intersection of dilution water control reference elevation 35
(FIG. 3A).
FIGS. 4 and 5 illustrate two variations of a switch 50 mounted in switch
containment housing 34 at dilution water control reference elevation 35. A
photoelectric switch 50A is shown in FIG. 4 and can be used with either
type of hydrometer apparatus 20 described above. A snap action switch 50B
is shown in FIG. 5 and can be used with piston type hydrometer 20A (FIG.
2).
Photoelectric switch 50A shown in FIG. 4 is comprised of a photoelectric
light source 52 and a photoelectric light receiver 54 located in diametric
opposition to retroreflective target 56. Photoelectric switch 50A is
connected to circuit 48 that provides energy source 46 to valve control
44. A light beam 58 is continuously emitted from photoelectric light
source 52 when energy source 46 is connected to photoelectric switch 50A.
Photoelectric switch 50A is positioned in switch containment housing 34 to
emit light beam 58 at dilution water control reference elevation 35.
Photoelectric switch 50A provides an open circuit 48 when a light beam 58
emitted from photoelectric light source 50 reflects off retroreflective
target 56 to photoelectric receiver 54 (FIG. 4). Photoelectric switch 50A
provides a closed circuit 48 when photoelectric receiver 54 does not
detect light beam 58 emitted from photoelectric light source 52 due to
adsorption of light beam 58 by hydrometer apparatus 20 (FIG. 4A).
Snap action switch 50B shown in FIG. 5 is comprised of a switch body 51 and
an activation lever arm 53. Snap action switch 50B is positioned in switch
containment housing 34 where activation lever arm 53 is slightly below
dilution water control reference elevation 35. Snap action switch 50B is
connected to circuit 48 that provides energy source 46 to valve control
44. Snap action switch 50B provides an open circuit 48 when activation
lever arm 53 is below dilution water control reference elevation 35 (FIG.
5). Snap action switch 50B provides a closed circuit 48 when activation
lever arm 53 is above dilution water control reference elevation 35 (FIG.
5A).
FIG. 6 is a detail illustration of the invention featuring piston type
hydrometer 20A and photoelectric switch 50A. As shown in FIG. 6, piston
type hydrometer 20A is suspended in equilibrium in caustic 12 contained in
catholyte reservoir 10 having outlet 14 at hydrometer base reference
elevation 39. Hydrometer sleeve housing 26 is mounted to catholyte
reservoir 10 below switch containment housing 34. Hydrometer sleeve
housing 26 is open with switch containment housing 34 and both provide
necessary position of piston type hydrometer 20A for communication with
photoelectric switch 50A mounted in switch containment housing 34.
Photoelectric switch 50A opens and closes circuit 48 that supplies energy
source 46 to valve control 44. Valve control 44 opens valve 42 when
circuit 48 is closed and closes valve 42 when circuit 48 is open. Valve 42
controls flow of dilution water 62 through inlet 16 connected to catholyte
reservoir 10. Hydraulic head pressure of dilution water 62 is higher than
the hydraulic head pressure of caustic 12 contained in catholyte reservoir
10 to allow flow of dilution water 62 into catholyte reservoir 10 when
valve 42 is open. FIG. 6 shows hydrometer 20A below dilution water control
reference elevation 35 providing an open circuit 48 to valve control 44.
FIG. 6A shows hydrometer 20A above dilution water control reference
elevation 35 providing a closed circuit 48 to valve control 44. Dilution
water 62 is supplied by a dilution water inlet 64.
FIG. 7 is a detailed illustration of the invention featuring emerged body
type hydrometer 20B and photoelectric switch 50A. As shown in FIG. 7,
emerged body type hydrometer 20B is mounted to the exterior of catholyte
reservoir 10 with open connection to the interior of catholyte reservoir
10 provided by access ports 25A and 25B. An outlet port 14A is connected
to emerged body enclosure 23 which provides means for displaced caustic 12
to exit catholyte reservoir 10.
Emerged body 21 is submerged in caustic 12 contained in emerged body
enclosure 23. Position of emerged body 21 is varied with density of
caustic 12. When density of caustic 12 is lower than density of emerged
body 21, the gravity force caused by the weight of emerged body 21 exceeds
the buoyant force caused by caustic 12 allowing emerged body 21 to
equalize at bottom of body enclosure 23. When density of caustic 12
exceeds the density of emerged body 21, the gravity force caused by the
weight of emerged body 21 is less than the buoyant force caused by caustic
12 allowing emerged body 21 to rise and equalize at emerged body stop 27.
Photoelectric switch 50A mounted in switch containment housing 34 is
fastened to the outside of emerged body enclosure 23 at a position
slightly below emerged body stop 27. Position of switch containment
housing 34 in relation to emerged body stop 27 provide the necessary
position for communication between emerged body 21 and photoelectric
switch 50A.
Photoelectric switch 50A opens and closes circuit 48 that supplies energy
source 46 to valve control 44. Valve control 44 opens valve 42 when
circuit 48 is closed, and closes valve 42 when circuit 48 is open. Valve
42 controls flow of dilution water 62 through inlet 16 connected to
catholyte reservoir 10. Hydraulic head pressure of dilution water 62 is
higher than the hydraulic head pressure of caustic 12 contained in
catholyte reservoir 10 to allow flow of dilution water 62 into catholyte
reservoir 10 when valve 42 is open. Dilution water 62 is supplied by a
dilution water inlet 64.
FIG. 7 shows emerged body 21 below dilution water control reference
elevation 35 providing an open circuit 48 to valve control 44. FIG. 7A
shows emerged body 21 above dilution water control reference elevation 35
providing a closed circuit 48 to valve control 44.
The invention can be further improved by adding two or more dilution water
control apparatuses 40 to hydrometer apparatus 20. FIG. 8 illustrates a
caustic density maintenance system with two dilution water control
apparatuses 40 featuring a photoelectric switch 50A and piston type
hydrometer 20A.
FIG. 8A illustrates a caustic density maintenance system with two dilution
water control apparatuses 40 featuring a photoelectric switch 50A and
emerged body type hydrometer 20B. When a second photoelectric switch 50A
is added to hydrometer apparatus 20, a secondary dilution water control
reference elevation 35' is developed. Multiple dilution water control
apparatuses 40 in either system provide backup to the dilution system in
the event of a failure experienced by one dilution water control
apparatuses 40.
Operation of Invention
It should be understood that FIGS. 6 and 7 depict the position of piston
type hydrometer 20A (FIG. 6) and emerged body type hydrometer 20B (FIG. 7)
when the density of caustic 12 in catholyte reservoir 10 is at an
acceptable level. It should also be understood that light beam 59 emitting
from photoelectric light source 52 at dilution water control reference
elevation 35 is reflecting off of retroreflective target 56, and being
detected by photoelectric light receiver 54. When photoelectric light
receiver 54 detects light beam 58, photoelectric light switch 50A provides
an open circuit 48 between valve control 44 and energy source 46. Since
energy source 46 is not provided to valve control 44, valve 42 on inlet 16
remains closed, and not allowing dilution water 63 to enter catholyte
reservoir 10.
It should be further understood that FIGS. 6A and 7A depict the position of
piston type hydrometer 20A (FIG. 6A) and emerged body type hydrometer 20B
(FIG. 7A) when the density of caustic 12 in catholyte reservoir 10 exceeds
the maximum desirable density limit. It should also be understood that
photoelectric light receiver 54 is not detecting light beam 58 reflecting
off of retroreflective target 56 since light beam 58 is intercepted by
piston type hydrometer 20A as demonstrated in FIG. 6A, and emerged body 21
of emerged body type hydrometer 20B in FIG. 7A. When light beam 58 is not
detected by photoelectric light receiver 54, photoelectric light switch
50A provides a closed circuit 48 between valve control 44 and energy
source 46. Since energy source 46 is provided to valve control 44, valve
42 on inlet 16 opens and allows dilution water 63 to enter catholyte
reservoir 10.
FIGS. 6 and 6A illustrate piston type hydrometer 20A and photoelectric
switch 50A. As the density of caustic 12 increases, buoyant forces on
piston type hydrometer 20A increase due to the change in specific gravity
of caustic 12. Since the gravitational force of piston type hydrometer 20A
remains constant, piston type hydrometer 20A rises as a result of the
increased buoyant forces caused by increasing density of caustic 12.
Therefore the vertical distance between the top of piston type hydrometer
20A and the surface of caustic 12 increases with increasing density and
decreases with decreasing density. This variable vertical distance is
referred as hydrometer differential elevation 38.
As the density of caustic 12 increases, piston type hydrometer 20A
continues to rise until the top of piston type hydrometer 20A intercepts
light beam 58 at dilution water control reference elevation 35 (FIG. 6A).
Photoelectric light receiver 54 no longer detects light beam 58, therefore
closing circuit 48 between energy source 46 and valve control 44. Closed
circuit 48 provides energy source 46 to valve control 44 which opens valve
42 and allows dilution water 62 to flow through inlet 16 into catholyte
reservoir 10. As dilution water 62 enters catholyte reservoir 10, caustic
12 is diluted and excess displaced caustic 12 exits catholyte reservoir 10
through outlet 14. Flow of dilution water 62 into catholyte reservoir 10
continues as long as light beam 58 is intercepted by piston type
hydrometer 20A.
As caustic 12 is diluted, the density of caustic 12 decreases causing
piston type hydrometer 20A to drop below dilution water control reference
elevation 35. When piston type hydrometer 20A drops below dilution water
control reference elevation 35, light beam 58 reflects off of
retroreflective target 56 and is detected by photoelectric light receiver
54. Since photoelectric light receiver 54 detects light beam 58,
photoelectric switch 50A opens circuit 48 between energy source 46 and
valve control 44. Open circuit 48 removes energy source 46 from valve
control 44 which closes valve 42 and stops the flow of dilution water 62
from entering catholyte reservoir 10 (FIG. 6).
The desired density range setting of caustic 12 in catholyte reservoir 10
is obtained by one of two methods when using piston type hydrometer 20A.
The first method is to change the specific gravity of piston type
hydrometer 20A by adding the appropriate amount of liquid 28 into enclosed
body 22 of piston type hydrometer 20A. The second method is to change the
activation differential elevation 37 by changing either hydrometer base
reference elevation 39 or dilution water control reference elevation 35
(FIGS. 2 and 2A).
FIGS. 7 and 7A illustrate emerged body type hydrometer 20B and
photoelectric switch 50A. Emerged body hydrometer 20B includes emerged
body 21 which is constructed of a material that has the same specific
gravity as caustic 12 at the maximum desirable density limit. When the
density of caustic 12 is below the maximum desirable density limit, the
gravitational forces caused by the weight of emerged body 21 exceed the
buoyant forces imposed by caustic 12, causing emerged body 21 to equalize
at the bottom of emerged body enclosure 23. As the density of caustic 12
increases, buoyant forces on emerged body 21 increase due to the change in
specific gravity of caustic 12.
When the density of caustic 12 exceeds the maximum desirable density limit,
buoyant forces caused by the increased density of caustic 12 exceeds the
gravitational forces caused by the weight of emerged body 21. The
excessive buoyant forces imposed on emerged body 21, lift emerged body 21
in emerged body enclosure 23. The excessive buoyant forces are overcome by
emerged body stop 27 which stops the vertical movement of emerged body 21.
As shown in FIG. 7A, emerged body stop 27 provides the necessary position
of emerged body 21 to intercept light beam 58 at dilution water control
reference elevation 35. Photoelectric light receiver 54 no longer detects
light beam 58, therefore closing circuit 48 between energy source 46 and
valve control 44. Closed circuit 48 provides energy source 46 to valve
control 44 which opens valve 42 and allows dilution water 62 to flow
through inlet 16 into catholyte reservoir 10. As dilution water 62 enters
catholyte reservoir 10, caustic 12 is diluted and excess displaced caustic
12 exits catholyte reservoir 10 through outlet port 14A. Flow of dilution
water 62 into catholyte reservoir 10 continues as long as light beam 58 is
intercepted by emerged body 21.
As caustic 12 is diluted, the density of caustic 12 is decreased and the
buoyant forces are overcome by the gravitation forces of emerged body 21,
causing emerged body 21 to drop below dilution water control reference
elevation 35. When emerged body 21 drops below dilution water control
reference elevation 35, light beam 58 reflects off of retroreflective
target 56 and is detected by photoelectric light receiver 54. Since
photoelectric light receiver 54 detects light beam 58, photoelectric
switch 50A opens circuit 48 between energy source 46 and valve control 44.
Open circuit 48 removes energy source 46 from valve control 44 which
closes valve 42 and stops the flow of dilution water 62 from entering
catholyte reservoir 10 (FIG. 7).
The desired density range setting of caustic 12 in catholyte reservoir 10
is controlled by the density rating of emerged body 21. The advantage of
using emerged body type hydrometer 20B over piston type hydrometer 20A is
that the dilution water control reference elevation is set independent of
the surface elevation of caustic 12 in catholyte reservoir 10. Therefore,
emerged body type hydrometer 20B can be used in a catholyte reservoir 10
that experiences variations in the surface elevation of caustic 12.
Conclusions, Ramifications, and Scope of Invention
As with the prior art, the novel apparatus depicted above provides an
automated means to prevent density of a caustic from exceeded an
unacceptable high concentration in the catholyte reservoir. In addition,
this invention provides means to maintain a lower acceptable concentration
of caustic solution to maintain the necessary catholyte conductivity. The
invention further provides increased reliability of the automatic dilution
operation by eliminating the plugging possibility of the dilution stream
nozzle described in the prior art, provides dilution water only when
required thus eliminating the need to recycle water and reduce the cost of
dilution water pre-treatment, and provides a means to add the dilution
water at a location that promotes natural mixing and a virtually
homogeneous caustic solution.
It will thus be seen that the objects set forth above, and those made
apparent from the foregoing description, are efficiently attained and
since certain changes may be made in the above construction without
departure from the scope of the invention, it is intended that all matters
contained in the foregoing description or shown in the accompanying shall
be interpreted as illustrative and not in a limiting sense. One example
would be to connect the dilution water control system to a telemetry logic
controller to allow centralized control of several dilution water control
systems.
It is also to be understood that the following claims are intended to cover
all of the generic and specific features of the invention herein
described, and all statements of the scope of the invention which, as a
matter of language, might be said to fall there between.
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